Rankink is running the 275s on an 8" wheel b/c he has to for the Stock Class rulings.
I saw "scooby south" with a set of 17x9 5Zigen FN01r-Cs at the Subie challenge in Gainesville, not sure on the offset though but they didn't appear to stick out very much (so I am assuming theing are +43 as Hoppe had the +35s on before and those stuck out more (but i could be wrong)), and with 1.5-2.5 degrees of camber the tire should be able to "tuck" into the fender if need be.
I'm running 255s on the stock wheels with STi Pinks and everything is perfect. Not sure why you would run anything less then 255s unless limited by class. I hope to get some 275s and some 17x9s but I need to do some more research on if they will fit, I'd be more then happy with a set of 255 Victos on those 17x9 5zigens though.